It was one of the highlights of the municipal calendar: every year the small market town of Bishop's Stortford would get together with its continental "twins" – the attractive towns of Friedberg in Germany and Villiers-sur-Marne in France.

Councillors discussed common problems: recycling, rubbish collection, and moaning constituents. There were cultural shows, family exchanges, and long-standing friendships forged over the odd glass of vin rouge and toasts to European brotherhood.

This September, however, the Tory-run town council took the dramatic step of "breaking off" diplomatic relations with the French and the Germans. By 13 votes to 3 the Conservatives decided to end more than 46 years of town-twinning. Letters are this week on their way to the French and German mayors informing them of the decision.

The vote appears to be the latest manifestation of grassroots Euroscepticism. Although no reason was given for the proposal to "de-twin", Lib Dems say it stems from a visceral Tory hatred for the European Union. Two other rightwing councils – Doncaster, south Yorkshire, and Wallingford in Oxfordshire – have in recent years also voted to kill off twinning arrangements.

"It's a strange decision. None of us could see it coming," Mike Wood, a Liberal Democrat councillor, told the Guardian mournfully. The vote on 19 September was, he suggested, a kick in the teeth to the entente cordiale and Anglo-German friendship: "It's indicative of modern-day Conservatives. They have this hangup about Europe."

Wood is the last surviving Lib Dem on the council, following his party's trouncing in May's local elections. (He opposed the de-twinning motion, together with one rebel Tory and an independent.)

He said the Tory-run council was generally pragmatic and avoided "outlandish" acts. But on this occasion, he said, it had suffered a moment of ideological lunacy. "They [the Tories] are usually normal people. But whenever you mention Europe or the European Union they turn into some kind of monster," Wood said.

"I think Euroscepticism has grown. You see this in many walks of life. You see it in this parliament," he said, referring to last month's Tory backbench rebellion, in which 81 MPs defied David Cameron to call for an EU referendum.

The council's gesture has saddened those who have worked hard to build up cultural ties. Maggie Groves wrote to councillors, pointing out that the twinning association was "still going strong", with 60 people at this year's Valentine's evening. She said became close friends with a French woman from Villiers – the daughter of Polish Jews who fled to France – who had overcome her prejudices against Germans thanks to twinning. "I cannot understand this decision. I am very distressed by it," she said, urging the council to reconsider.

Town-twinning began in the UK more than a century ago, but it was after the second world war that the idea of municipal co-operation flourished as a way of promoting reconciliation and healing wartime divisions.

The logic was clear: bombed-out Coventry was twinned with Stalingrad and Dresden. There are tens of thousands of agreements across Europe with more than 2,000 in the UK.

Bishop's Stortford is, meanwhile, no Thatcherite ideas lab but a pleasant Hertfordshire commuter town. It has a population of 35,000. It is close to Stansted airport and the M11. It has a small ruined castle – actually, more of a glorified hill – as well as Cecil Rhodes's birthplace, and the ancient medieval forest of Hatfield. The royal hunting ground is popular with riders, dog-walkers and middle-class foragers. There is even an acclaimed state school, Hockerill Anglo-European College, which specialises in teaching and French and German.

The town's partners are similar in size, and are also run by conservative parties. Villiers-sur-Marne is a dormitory suburb of Paris, close to Disneyland Paris; Friedberg a satellite of Frankfurt, Germany's banking and commercial hub. The town was the birthplace of Erasmus Alberus, a humanist and friend of Martin Luther's. It has a Disney-style 14th-century castle, and a website proudly mentioning its "Partnerstadt" links. Bishop's Stortford twinning association had its own illustrious patron – the sculptor Henry Moore. Moore, who lived and worked in the village of Much Hadham: "I am a staunch believer in European co-operation."

Jan Richardson, vice-chair of the twinning association, said councillors dipped into their own pockets to pay for annual meetings. They travelled on budget flights, and stayed free of cost with local families.

The argument that the internet and easier travel made twinning an anachronism was wrong, she said. "I've heard the argument [against twinning] that everybody goes to Europe anyway. But this is different. You learn about the way people live. It's different," she said.

Labour hasn't had a seat on the town council for nine years. But Denis MacShane, the Labour MP and former Europe minister, said he was dismayed by the rise of anti-European sentiment across the country: "Municipal isolationism is the latest and saddest manifestation of Tory pathological obsession against Europe," he observed.

He argued: "Town-twinning is a low-cost way of linking schools, civil society, local arts and sports clubs and learning about each other across frontiers. The Conservatives really do want to shut Britain down from contact with the rest of the world."

Bishop's Stortford's Conservative leader, John Wyllie, denied this. He claimed the council ended links with the continent because of "lack of interest".

The twinning committee would continue but the council would no longer be involved, he said. He admitted he had missed out on trips to Friedberg and Villiers-sur-Marne when he was mayor, but joked: "I'm not bitter and twisted."

Asked whether Euroscepticism lurked behind the decision to dump the Europeans, Wyllie was indignant. "It had nothing to do with that. This is just typical Lib Dem rhetoric. They are playing party politics," he said. He added sarcastically: "It's nice to see that they [the Lib Dems] have their finger on the pulse. People are losing their jobs in this town and all they care about is twinning."

Wyllie said he and his Tory colleagues had reached the conclusion that twinning was no longer "relevant" in today's society. He said that the town's thriving schools already had regular exchanges with other European cities. And what of the letter sent to the French and the Germans telling them of the decision? "It was polite," he said.

Michael Keller, Friedberg's mayor, said he wasn't surprised by the council's decision. "The partnership has been on its last legs for the past 10 years. We got hints in 2005 they were keen to end it. Not enough young people have been involved. These days they go to China, Russia and the US."

He added: "Twinning began for us in 1965. Those involved had personally experinced the catastrophe of the second world war. This isn't so relevant today. The world has changed. Europe needs new impulses."

Keller said he would now talk to the French to see what they thought. "I suspect English Euroscepticism played a role also. I would have preferred it if we'd ended twinning with a big party rather than just a letter."